1. Technical Field
The technical field relates to an imaging apparatus and a camera that include a function of enabling focus detection at high speed while exposing the image sensor to light.
2. Description of the Related Art
Recently, digital cameras for converting optical images into electrical signals using image sensors such as CCD (Charge Coupled Device) or CMOS (Complementary Metal-Oxide Semiconductor) sensors and digitizing and recording the resulting electrical signals, are becoming popular.
Single-lens reflex digital cameras include a phase difference detecting unit that detects phase differences and employs an auto focus function (AF function) based on a phase difference detecting scheme. According to the auto focus function based on a phase difference detecting scheme, the defocus direction and the degree of defocus can be detected, so that there are advantages of reducing the time to move the focus lens and adjusting focus at high speed. For example, see Patent Document 1 (Japanese Patent Application Laid-Open No. 2007-163545). To guide an optical image of the subject to the phase difference detecting unit, conventional single-lens reflex digital cameras are provided with movable mirrors that can be inserted on and evacuated from the optical path from the lens barrel to the image sensor.
To realize miniaturization of digital cameras, so-called compact digital cameras employ an auto focus function based on a video auto focus scheme (video AF scheme) using image sensors. See, for example, Patent Document 2 (Japanese Patent Application Laid-Open No. 2007-135140). Miniaturization of compact digital cameras is realized by removing mirrors. Further, compact digital cameras can operate the auto focus function while exposing the image sensors to light and shoot images while displaying images shot by the image sensor in the display section provided in the back of the camera. This auto focus function based on the video AF scheme provides an advantage that the precision is generally high compared to auto focus based on the phase difference detecting scheme.
However, with the single-lens reflex digital camera disclosed in Patent Document 1, movable mirrors that move from the lens barrel to the image sensor are inserted on the optical path to guide the optical image of the subject to the phase difference detecting unit. Therefore, it is not possible to use the phase difference detecting unit while the image sensor is exposed to light.
Further, the above video AF scheme used in the digital camera disclosed in Patent Document 2 cannot detect the defocus direction. For example, although, with the auto focus function based on a contrast scheme, a contrast peak is determined when focus is detected, the direction of the contrast peak, that is, the defocus direction cannot be detected unless the focus lens is moved forward and backward from the current position. Therefore, detecting focus at higher speed is limited to a certain extent.